Metal corrosion is a problem in the petroleum industry which persists from the well-head, through refining operations, and into storage of purified materials. Among the operations where corrosion is a constant menace to the structural integrity of equipment is production of petroleum at the well, secondary petroleum recovery through water flooding, storage and transportation of crude oil, refinery operations such as distillation, condensation, heating, catalytic cracking and reforming, and transportation and storage of refined petroleum products. The successful operation of many of these processes are dependent upon the use of corrosion inhibitors to minimize equipment replacement costs and lost time associated with necessary maintenance and repair.
There is no single causative factor in promoting metal corrosion, although the presence of water, even if only in relatively small quantities, is a common denominator. Perhaps the most pernicious material promoting corrosion is hydrogen sulfide. Whether present per se, or produced from organic sulfides in various refining operations, hydrogen sulfide may be present in petroleum and petroleum products from the well-head through the refinery. Another common source of corrosion is dissolved salt, i.e., brine, which is particularly acute at the well-head. Still another common source is dissolved oxygen. Other agents either normally present in petroleum, or produced during its processing, which contribute to corrosion are hydrogen chloride, carbon dioxide, and carboxylic acids. Additional factors to be considered are the acidity (pH) of the corrosive media and the temperature at which metal surfaces are exposed to corrosive media.
As there is no universal causative factor in promoting corrosion, so there is no universal panacea in inhibiting corrosion. Perhaps the single most important class of chemical agents useful as corrosion inhibitors to the petroleum industry is the class of organic nitrogen compounds. Examples include: N-alkyl propylenediamines, U.S. Pat. No. 2,736,658, and their salts with fatty acids; imidazolines and tetrahydropyrimidines, U.S. Pat. No. 3,020,276; polyethoxylated amines and amides; and various succinic anhydrideamine condensation products, U.S. Pat. No. 3,347,645. Although great strides have been made in affording protection to metals against the corrosive agents encountered in the petroleum and related industries, there remains a need for corrosion inhibitors which will appreciably lengthen the lifetime of metallic components used in various operations and which will minimize down-time associated with remedying difficulties traceable to corrosion. It is of prime importance that such corrosion inhibitors remain cost-effective while displaying superior inhibitory properties.